Answer:
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Answer:
a. antigen
Explanation:
The Immune system is composed of immune cells  that  defend the body against foreign substances such as bacteria or virus. Lymphocytes (B and T cells) are one of the main immune cells
Lymphocytes have the ability to recognize and bind to antigens, wich are substances foreign to the body ( i.e bacterial or virus elements) that evokes an immune response. 
 
        
             
        
        
        
Answer:
C
Explanation:
The gravity of the sun and moon pull on the water of the oceans of the earth hence causing a bulge of these waters at the point on earth where the moon is above. The region where the moon is above, and the opposite side on the earth, will therefore experience high tides while the places at right angles (on the surface of the earth in relation to the moon position) will experience low tides. 
 
        
             
        
        
        
Diffusion is the movement of molecules from an area where they’re at a higher concentration to areas that have a lower concentration - goo gle